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Slab Settlement And Why It Happens

Monday, December 14th, 2020 by Kinsey Price


What exactly is slab settlement?

Slab settlement is simply the movement a concrete slab experiences when the soil underneath it can no longer support the weight of it.

Soil changes - that is why your concrete will begin to sink and settle. Let's focus on the three most common reasons why a concrete slab will settle.

1. Changes in the soil's moisture content

Two very common soil types are sandy soil and clay soil. Sand is not greatly affected by moisture, but it does eventually wash away.

When wet, clay holds water and expands in size; when dry, it does the opposite…it shrinks. Soil dries out for many reasons: drought conditions, tree roots taking up all of its moisture, and leaking HVAC systems under your floor slabs. When soil beneath your concrete slab shrinks, it creates empty space for the concrete slab to settle into. This creates cracks and unleveled concrete.

two foundation slabs not flush or level

2. Wash-out of soil under the slab

As water moves beneath your concrete slab, it can wash away the soil supporting the concrete. This is caused by plumbing leaks, erosion, large rains, and numerous other reasons. If water continues to wash underneath concrete, it will eventually leave nothing left to support the concrete…resulting in sinking and caving.
Foundation cracks in the base of the external foundation

3. Poorly compacted fill soil

When a home is being constructed, the soil is usually moved around or spread out to make sure the whole plot is at the desired grade level. When the concrete slab is poured on top of this loose soil, it compresses and settles the soil. When the soil moves like this, it causes concrete to crack and sink.
cement on the side where a vacant area is by the stairs

Many issues such as these, and others might be affecting your home or commercial structure. The foundation specialists at Fortress in Front Royal, Bentonville, and the surrounding areas will be able to diagnose these issues and more with a free written evaluation and in-home foundation inspection.

Call us today at 1-844-877-3244 or contact us online for a free estimate!

our service area

We serve the following areas

Our Locations:

Fortress Foundation Solutions
147 Mill Ridge Rd #234
Lynchburg, VA 24502
1-434-207-5599


Fortress Foundation Solutions
5305 Jefferson Pike
Frederick, MD 21703
1-301-234-7042
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